INBREEDING ENDANGERS WILD CHEETAH

The world`s fastest animal, the cheetah, may have reached an evolutionary dead end, leading American biologists say.

They have discovered that cheetahs in South Africa--one of the two last strongholds for the species--are so inbred that they are in danger of extinction.

The extent of this inbreeding was revealed by biologist Dr. Stephen O`Brien of the National Cancer Institute when he and colleagues recently carried out a series of skin grafts on six pairs of unrelated cheetahs.

Most animals normally reject skin grafts that come from unrelated donors. But the scientists found in their tests that each cheetah accepted the foreign graft as if the skin were its own.

This failure by the body to recognize foreign tissue, the biologists say, reveals that South African cheetahs must be very similar in their genetic make-up.

Without genetic diversity, cheetahs must now be highly vulnerable to diseases that could wipe out large numbers of them, or even cause their extinction.

The scientists suspect that this inbreeding may have led to a viral epidemic at an Oregon safari park in 1983 in which 18 cheetahs died, although all other big cats were unaffected. All the cheetahs came from South Africa.

The scientists say they do not know how cheetahs became so inbred, though they suspect that intensive hunting of the animal in the last century may have reduced populations to a handful of survivors. Bred from these, today`s cheetahs would be genetically identical.

Now the team has begun a similar investigation of cheetahs in East Africa --the other main stronghold--to see if similar inbreeding exists there.